1. Field of the Invention
The present invention relates to a method of forming an image on an image forming material, and in particular, to an image forming method useful for a planographic printing plate precursor capable of direct plate-making by scanning a printing plate precursor using an infrared laser beam based on digital signals from a device such as a computer.
2. Description of the Related Art
The development of laser technology in recent years has been remarkable, and a small high-power laser element can be easily obtained as a solid laser element or a semiconductor laser element that emits infrared rays of wavelengths of, in particular, 760 to 1200 nm (hereinafter also referred to as “infrared laser”). These infrared lasers are very useful as recording light sources for direct plate-making from digital data outputted from devices such as computers. Accordingly, there is an increasing need in recent years for an image recording material highly sensitive to light emitted from such infrared recording light sources, that is, an image recording material having a layer whose solubility in a developing solution significantly changes due to factors such as photochemical reactions arising from infrared laser beam irradiation.
Image recording materials capable of recording with such infrared lasers include those comprising an onium salt, resol resin, novolak resin and an infrared absorbing agent (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 7-20629); and an image forming material comprising haloalkyl-substituted s-triazine, resol resin, novolak resin and an infrared absorbing agent (see, for example, JP-A No. 7-271029).
Meanwhile, methods of exposing these image recording materials to light include a light exposure method intended to improve productivity by shortening the time necessary for light exposure, for example, a method of exposure to light at low resolution. Specifically, a method of exposure to light at a resolution of 1300 dpi or less is used in the field of newspaper printing.
However, the image-forming ability of image recording materials obtained by exposure to light at low resolution is inferior to the image-forming ability of materials obtained by exposure to high-resolution light of 2000 dpi or more, and for example, when the technology is applied to a method of making a printing plate from a planographic printing plate precursor, there is a problem in that the printing durability of the resulting planographic printing plate deteriorates when printing.
Image forming materials having a negative type polymerizable photosensitive layer, to which the method of the present invention is applied, may result in a lowering of polymerizability due to the influences of, particularly, oxygen or moisture in the air, and from this viewpoint, there is a demand for an image forming method capable of achieving a rapid and reliable curing reaction.